1. FIELD OF THE INVENTION
This invention relates generally to medical appliances; and more particularly to a safety guard for preventing accidental puncture by a used medical needle.
2. PRIOR ART
As is well known, medical needles serve a myriad of very important medical functions. Throughout the medical community, the severe problem which has developed in relation to use of such needles is also known.
That problem arises from the continuing presence of horrible diseases such as acquired immune deficiency syndrome ("AIDS") and hepatitis, which can be transmitted by exchange of bodily fluids between people. These diseases have led medical institutions to exclusively use disposable needles, syringes and phlebotomy sets to inject medication and to withdraw blood.
A severe residual risk remains, however, for medical personnel themselves in the inadvertent touching of needle tips after withdrawal from infected patients. Medical needles are designed and manufactured specifically to be extremely sharp and to puncture skin and flesh with only the slightest pressure.
As a result, what would ordinarily be an inconsequential scratch or pinprick can bring and has brought severe disease or even death to many medical staff members and others who have become infected after such scratches. Needless to say, health-care professionals are well aware of this risk and take considerable precautions to avoid such inadvertent punctures; thus the risk is reduced on a probability basis to an exceedingly small value.
Nevertheless, the exposure is so massive for working doctors, nurses and technicians that occasional punctures are inevitable. As a practical matter, it is virtually impossible for such an individual to reduce the incidence of accidental puncture to less than, say one every year or perhaps one every few years.
Of course, not every such puncture follows contamination of the needle by a patient carrying a transmissible fatal disease. Nevertheless, there are enough medical personnel and enough such patients that a significant number of medical staffers die--and of course a greater number become very sick--from these accidents.
Sometimes a person using a medical needle has only one hand free to hold the needle prior to properly sheathing it. Since sheathing is most easily performed with two hands, the difficulties inherent in the use of a simple sheathing cap are significant.
Furthermore, possibly ten to twenty percent of needle use occurs in a tense hectic setting or environment where time is short and long laborious precautions can seldom be taken. For instance, learning situations, emergencies and/or a patient's mental or physical condition may complicate needle use. In many situations when other operations need to be performed concurrently, even sheathing can be difficult.
Despite the difficulty, medical staff members who frequently use hypodermic needles and the like have become adept at sheathing needles with one hand. Heretofore this has been the simplest and least problematical solution to a continuing problem.
Nevertheless, the use of sheaths is a very poor solution. The movements involved in sheathing a needle are precisely the kind that sooner or later go astray, leading to an occasional scratch or puncture and thereby statistically to severe illness or death.
Devices which have been introduced to provide added protection against punctures by contaminated hypodermic needles fall into two general design categories. Some devices have protective mechanisms which encase or emanate from the syringe body, while others are associated with the needle itself.
U.S. Pat. No. 4,592,744 to Janine C. Jagger et al. discloses a protective mechanism encasing almost the entire syringe. In this device, the needle is mounted by a relatively tight press fit to the forward end of a syringe that is fitted within a handle. The needle also extends in a relatively loose press fit through a hole in the front of the handle.
After use, the syringe must be pulled bodily out of the back end of the handle, carrying the needle rearward out of its front-end press fit with the handle, and into the cavity within the handle. The needle is carried in a flange that is too wide to escape from the rear end of the handle, and accordingly is pulled away from its tight press fit to the front end of the syringe. Thus the needle is trapped within the handle.
In the phlebotomy device, the blood-collection receptacle is initially enclosed within an outer housing/handle during use. The rear of the needle passes in a tight friction fit through an elastomeric stopper on the receptacle.
Thereafter, the receptacle is used as a tool to unscrew the needle from the forward end of the handle. Then the receptacle stopper, with embedded needle, is pulled off the rear end of the needle so that the receptacle with its blood sample can be removed from the handle.
Thus the two forms of the Jagger invention that are described require the user to perform elaborate compound manipulations including retracting the entire syringe, or double phlebotomy needle, all the way back through the hole in the handle. These maneuvers are all but impossible to accomplish using only one hand. The difficulty will be compounded if the maneuver must be performed with only part of the user's attention, as is often the case.
In most instances the necessary manual operations must include several motions in sequence. What is required is a compound motion, each stage of which is typically of relatively large amplitude in comparison with the length of the needle and the size of the user's hand.
As a matter of ergonomics, the requirement for such large-amplitude and compound motions is inherently adverse to definite, reliable and therefore safe retraction. This is particularly so for medical personnel under harried circumstances.
Other factors, specific to the hypodermic and phlebotomy applications of the Jagger invention, make the procedure even more awkward and difficult. First, as to the Jagger hypodermic needle, proper retraction depends upon maintenance of the design relationships between two friction levels. These relations are too easily upset.
For example, they can be disturbed by temperature variations in storage, beyond the knowledge of the person using the device. They can also be disturbed by leakage of congealable or sticky substances such as blood or sucrose solution, through the large opening at the rear of the handle and into the exposed seams between the handle and the needle flange.
The necessary friction relationships can also be disturbed by imperfect insertion of the syringe tip into its mating receptacle at the rear of the needle flange. That procedure, which in many cases is performed by medical technicians on site, rather than the manufacturer's personnel, can at least in principle damage either of the friction-fitting surfaces involved.
In such circumstances the syringe can be extracted from the needle flange before the needle is retracted--leaving no proper means for retraction.
As to the Jagger phlebotomy needle, the arrangement for retraction is even more adverse to reliable operation. The flange of the phlebotomy needle must actually be unscrewed before it can be pulled back into the handle.
Other prior patents describe devices for automatic or semiautomatic resheathing of hypodermic syringes. U.S. Pat. No. 4,026,287 to Haller is among the better of these devices since it at least provides for retraction of the used needle into a cavity in a unitary, sturdy structure.
That device functions by screwing the plunger into the front of the syringe after use, to destroy a frangible seal that encircles the front of the syringe. Then the needle, which is still attached to the separated front of the syringe, is pulled back by the plunger into the barrel of the syringe. Once again, such elaborate manipulations are problematic in a hurried environment.
Further, Haller's device fails to protect against inadvertent insertion of fingertips into the syringe barrel Even more serious is the fact that Haller's syringe plunger can remain in place, held only by detents at the rear of the barrel. The Haller plunger thus remains dangerously ready to drive the needle forward again if the syringe is accidentally jarred past the detents.
In addition, Haller's device and many of the others discussed below are disadvantageous in that their after-use sheathing configurations are longer than the initial or before-use configurations. When disposed, the longer lengths can be dangerous: they are more susceptible to lateral forces, which cause breakage, than are shorter protective devices.
Mitchell, in U.S. Pat. No. 4,631,057, discloses a device in which a needle guard extends from its retracted position on the syringe body to its activated position around the needle shank. The needle guard is secured in that position by interlocking members. One member is on the needle guard, and the other is on a collar which is mounted to the syringe body.
This device has the disadvantage of leaving the unsealed forward end of the needle guard accessible to fingertips even in the activated position, as with the Haller device. Mitchell's needle guard, however, is more objectionable in this respect since its inside diameter is even larger than that of the syringe. Mitchell's device also shares with the Haller device an undesirable sensitivity to jarring the device out of its safety detents, and an extended after-use configuration.
Other patented devices with a like vulnerability to jarring out of detents and a like extended postuse configuration, but at least providing better frontal shielding against fingertip insertion, are U.S. Pat. Nos. 4,573,976 (Sampson), 4,643,199 (Jennings, Jr. et al.) and 4,643,200 (Jennings, Jr.)
Worthy of mention for its provision of more positive resistance to jarring of the needle out of its retracted position is U.S. Pat. No. 4,425,120 to Sampson et al. That device pays for its better safety locking with complexity of the manual manipulations required in use.
Similar observations apply to U.S. Pat. No. 3,890,971 to Leeson, which offers relatively very compact and stable postuse configuration, but at the cost of a relatively complicated mechanism and large-amplitude motions to effect the resheathing.
Each of these protective mechanisms that are associated with the handle or barrel of a device suffers from a lack of adaptability. Since syringe and phlebotomy devices come in many sizes and shapes, most or all of the protective mechanisms must be specially designed and fitted to the handles or barrels by the manufacturers.
Possibly within the other design category of protective devices--mechanisms associated with the needle rather than the body or barrel--are U.S. Pats. No. 2,876,770 (White), 2,674,246 (Bower) and 3,134,380 (Armao). These devices may appear to provide a protective enclosure for the needle, but they actually provide merely visual shields.
The designs of these shields were aimed mostly at alleviating a patient's fear of an injection. Before use, patients see only the shields. While the needles are still hidden from view, and before the needles actually puncture the skin, the shields apply pressure to the patients in the areas to be pierced. The patients benefit psychologically from concealment of the needles, and physically from the so-called "pressure anesthesia" effect. All this allows the injections to be made more easily.
Although these devices do have housings that enclose the needles, they do not protect against accidental punctures by used needles. In reality, the designs are conducive to such accidental punctures and for the present purposes counterproductive, since they effectively conceal the presence of dangerously sharp and possibly contaminated needles.
One device that provides more than just a visual shield is the ICU High Risk Needle, produced by ICU Medical Inc. Like the visual-shield devices, the ICU unit is associated with the needle rather than the syringe.
The protective sheath is a ribbed cylinder of hard plastic. This cylindrical sheath locks to a plastic sleeve that is snugly fixed along the needle shank.
This design requires a needle whose overall length is over twice that of the usable portion of the needle. The extra length is necessary mostly to accommodate the sheath, and also to provide for a proper locking mechanism of the sheath over the needle.
The locking mechanism consists of an internal flange at the rear of the movable sheath, and a groove formed between two thickened portions of the fixed sleeve. The internally flanged end of the sheath is notched, allowing the flanged end to spread apart and so pass over the thickened portion of the needle.
Once the internal flange is pulled onto the thickened portion, the flange seats in the groove and locks the sheath in place. The ICU device does not directly rely on attachment with the syringe body to function.
The extra needle length makes the ICU needle far more cumbersome than standard needles. In fact, the required lengths become limiting factors in the use of this device. For instance, if a needle with a usable length of five to six inches is required, the needle must be a foot long--usually impractical.
Even when the extra lengths are still within an acceptable range, they are very susceptible to accidental breakage--exposing sharp and jagged steel that is likely contaminated with blood. Such breakage can be caused by laterally applied forces during use and disposal. Moreover, these special and longer needles are not the type generally stocked, which means that they must be made and ordered specially.
Furthermore, the ICU design requires a different sheath length and a different sleeve length, for every needle length. A different sleeve is also required for every needle gauge.
Although needles are in a sense more regular and standardized than syringe and phlebotomy-set barrels and handles, nonetheless needles come in perhaps a thousand combinations of length, gauge, tip configuration, and manufacturer. The ICU strategy is limited to those relatively few needle configurations whose sales volume by a single manufacturer justifies design of molds and fixtures for individually compatible sheaths and sleeves.
Hence the ICU design fails to take effective advantage of the potential for standardization offered by associating the sheath with the relatively featureless needle.
Finally, the protective sheath on the ICU device has a relatively large opening near the needle tip. It provides a protective barrier only by extending approximately one-quarter inch past the needle. Therefore, some people's fingers may still be inserted into the opening.
In summary present protective devices generally are not adaptable to the wide range of syringes and needles which are usually stocked by hospitals and doctor's offices. Also, the majority of devices--both those associated with the syringe and those with the needle--are awkward or impossible to use with one hand, and leave the needle exposed to insertion of fingers through the guard.